The present disclosure relates to a recording apparatus that performs recording (light exposure) to an optical disc master, a master manufacturing apparatus for applying a development process on the exposed optical disc master to create a recorded master, and an optical disc recording medium manufacturing method for manufacturing an optical disc recording medium onto which recording information (a concave and convex pattern) is transferred based on the recorded master.
Japanese Unexamined Patent Application Publication No. 2009-70458 is an example of the related art.
For example, in an optical disc recording medium such as a CD (Compact Disc), a DVD (Digital Versatile Disc), or a BD (Blu-ray Disc: registered trademark), as is known as a so-called ROM type, there is a medium on which information is recorded by a combination of pits and lands. That is, information is recorded by formation of patterns of a concave portion as a pit and a convex portion as a land.
In manufacturing of the optical disc recording medium of the ROM type, firstly, a laser beam irradiation is performed on an optical disc master formed with a photosensitive layer to perform the information recording. Moreover, the development processing is performed on the optical disc master subjected to the recording process to create the recorded master formed with the pits, a stamper is created onto which the pit pattern (and recording information) formed on the recorded master is transferred, then, a substrate is created in which the recording information is reproduced by injection molding using the stamper or the like, and the film formation of a reflective film or the like is performed on the substrate, thereby manufacturing the optical disc recording medium.
In the manufacturing process of the optical disc recording medium, in recent years, a PTM (Phase Transition Mastering) type has been adopted in the recording process (a mastering process) so as to respond to a high recording density of the optical disc recording medium. The type is a so-called thermal recording.
In the PTM type, an inorganic resist is used as a photoresist that constitutes the photosensitive layer. Furthermore, a semiconductor laser is used as a recording laser.
Herein, in a type of the related art that does not adopt the PTM type, a gas laser or the like is irradiated by the use of an organic resist as the photosensitive layer. In this case, since the light exposure of the photoresist is a so-called optical recording, a portion exposed by laser becomes the pit as is. That is, the laser spot diameter directly affects the pit width as is.
On the contrary, in the PTM type, since heat is given due to the irradiation of laser beams, the characteristics of the inorganic resist are changed (that is, a chemical property is changed) and a recording mark is formed. In an inorganic resist used in the PTM type, a considerable chemical property change is indicated in a portion where heat is concentrated, and the size of a groove to be formed does not directly depend on the laser spot diameter. That is, in this respect, the PTM type is able to perform a groove formation that is finer than the type of the related art.
In the mastering of the PTM type, a recording waveform is used which takes into account the characteristic of the thermal recording.
FIG. 6A shows an example of a recording waveform corresponding to the thermal recording.
The recording waveform of this case includes a land pulse Pln, a recording waveform portion Pr, and a cooling pulse Pc that is inserted between the land pulse Pln and the recording waveform portion Pr as shown in the drawing.
The recording waveform portion Pr is a waveform portion that has a pulse of high power for forming the pit by the thermal recording. In addition, FIG. 6A shows that the recording waveform portion Pr has a single pulse and a constant power, but, in fact, for example, it is necessary that the recording waveform portion Pr is constituted by a more complex pulse depending on the pit length to be recorded.
The land pulse Pln is a pulse for forming the land portion, and is a pulse for adjusting the overall quantity of heat for assisting the thermal recording of the pit portion. The power may be at least set to be lower than the power at which the pit is formed.
In this case, it is characteristic that the cooling pulse Pc is inserted between the recording waveform portion Pr and the land pulse Pln. In the cooling pulse Pc, as the power thereof, power lower than that of the land pulse Pln is set. By the insertion of the cooling pulse Pc, it is possible to obtain an effect of increasing the contrast of the pit/land boundary in both of a front side edge and a back side edge of the pit formed on the optical disc master.
Furthermore, according to the recording waveform shown in FIG. 6A, by obtaining the land pulse Pln of a power higher than that of the cooling pulse Pc, it is possible to obtain an effect of suppressing an occurrence of a lack of heat due to the insertion of the cooling pulse Pc, particularly, at the front edge side, as a so-called preheat effect.